The hazards of nitrogen oxides and other compounds present in flue gases have resulted in the imposition of strict standards limiting discharges of such chemical species. To meet these standards, it is generally necessary to remove at least part of these oxides and/or other chemical species present in exhaust gases from stationary or mobile combustion sources.
Denitrification or selective catalytic reduction (SCR) technology is commonly applied to combustion-derived flue gases for removal of nitrogen oxides when passed through a catalytic reactor. The denitrification reaction comprises the reaction of nitrogen oxide species in the gases, such as nitrogen oxide (NO) or nitrogen dioxide (NO2), with a nitrogen containing reductant, such as ammonia or urea, resulting in the production of diatomic nitrogen (N2) and water. Moreover, various absorbent or capture technologies are used to remove other chemical species of a flue gas that are not catalytically decomposed.
The terminology catalytic reactor is generally used to describe a vessel comprising catalyst. Catalytic reactors generally comprise catalyst structures containing exhaust gas flow paths that enable contact between the exhaust gas streams and catalytically active components of the catalyst structure. The catalyst structure of a modular catalytic reactor is typically composed of one or more catalytic layers with each layer comprising a large number of modularized sections. Each modularized section further comprises a metal support framework which holds a number of catalyst bodies in place wherein sealing or packing materials between the catalyst bodies are used, if necessary, for proper flow distribution of exhaust streams passing through the catalyst bodies. The catalyst bodies contain the catalytic composition and display a physical structure that delineates flow channels or passageways for exhaust gas flow through the catalyst bodies.
In many cases, exhaust gas streams flowing through modularized sections of a catalytic reactor experience pressure drop. Pressure drop can result from structures, frictional forces and other factors impeding or resisting the flow of the exhaust gas stream. Pressure drop can result in various inefficiencies and cause parasitic power losses during industrial applications such as electrical power generation.